Disclaimer: I am not JK Rowling; none of it is mine.
"I'm dying, Harry."
"You're what?"
"Dying."
"Ha, ha."
"Harry I really am-"
"No-you are not dying, stop saying that. I don't understand. Why? How?"
"Voldemort is a monster, Harry."
"I know, that's why I killed him, but you're safe now. He can't hurt you!"
"Harry, he cast a spell on me."
"A spell? What kind of spell?"
"He wanted you to have a baby."
"A baby? Why?"
"He wanted an heir."
"Oh… What does that have to do with you, though?"
"I'll tell you, but stop interrupting."
Harry nodded in agreement.
"He wanted you to have a baby. He needed the child to have two very strong fathers. He chose me as the other father, but he knew I wouldn't rape you. So he cast a spell on me. If we don't have sex, I will die. But, the first time we have sex, you'll become pregnant."
"…That's why you're dying? You didn't have sex with me? Why didn't you say something? How much longer do you have?"
"I didn't want to pressure you into anything. You are the only true friend I have ever had on the light side. You don't know how much your support helped me stand against my father and do the right thing. The only reason I am telling you now, is so that when I go home tomorrow, to die, you won't wait for me to come back, because I'm not coming back after I leave."
"Do you want to die?"
"I have accepted my fate."
"Do you WANT to die?"
"Of course not, but I'm not forcing you to have sex with me and become pregnant."
"Why not?"
"For the love of Merlin, Harry. I love you, so much so that I feel like I'm drowning. I'd never hurt you, never force you to subject yourself to a pity fuck."
"Dragon, it would never be a 'pity fuck'."
"Yes, it would be."
"No. I, wow, why is this so embarrassing? I have wanted you for a long time."
"You have?"
"Ever since you pinned me against the wall outside DADA and confessed that you wanted to change sides."
"But, that was almost seven years ago."
"I know."
"Are you sure about this? I wouldn't hold it against you if you don't want to have sex with me."
"I don't want to have sex with you."
"…"
"I don't want to just have sex with you. I want to be with you, marry you and raise my child with you. You're all I have left of those years. You're all I need, as long as you stay with me."
"Harry I-"
"Just stay with me forever."
"I promise, forever, until the stars run out."
A little sappy, but oh well. It's fast. Harry and Draco have been close friends for a long time, after they both lost everyone to the war.